Manitoba officials were working quickly Monday to build higher dikes along the Assiniboine River, while their counterparts in Saskatchewan warned that flooding would remain a threat for the rest of the month.

For the past week, much of the Prairie provinces has been flooded or in danger of being so, with parts of the region seeing the highest water levels in 150 years.

About 700 people in Manitoba have already been forced from their homes, dozens of roads have been closed, and officials are urging more vigilance.

"Many of the crests are some time off," Emergency Measures Minister Steve Ashton said on Sunday. "We're not even necessarily at the end of the beginning of the spring flood stage."

One of the province's major trade routes, Highway 75, was closed Monday because rising water on the Red River and its tributaries made it impassable.

Truckers heading to the U.S. are being forced to make extensive detours due to the closure. 

Dikes along the Assiniboine upstream of Winnipeg were built to withstand water levels seen in 1976, the worst year on record. But the river was ice-free that year, and officials worry that ice jams this year will make water levels worse than they would otherwise be.

Officials said the water level dropped overnight on the Assiniboine in Brandon, but flood watches are still in effect from Russell to Portage la Prairie.

300-flood-lumsden

A small house is seen near flood waters in Lumsden, a small town north of Regina. ((David Stobbe/Reuters))

"We have not had a dike breach at this time — just over-topping," Steve Topping with Manitoba Water Stewardship said. "Equipment is following the ice jam as it progresses down the stream and they're raising the dikes to contain the waters.

Temperatures are forecast to rise this week, so more snowmelt is expected.

Saskatchewan officials call for vigilance

The forecast peaks for the Assiniboine River have increased because of the snow and rain that fell across Saskatchewan over the weekend, CBC News meteorologist Johanna Wagstaffe said.

Flood worries resulted in states of emergency being declared on the weekend in the Manitoba municipalities of St. François Xavier, Cartier and Headingley.

The community of Wawanesa is expected to get a second crest, likely next week, and a high-water advisory has been issued for the Gladstone area because of a second crest expected on the Whitemud River in the next few days.

The worst case scenario for flooding does not appear to be materializing, but officials are calling for vigilance. The Saskatchewan Watershed Authority said many water flows in the southern half of the province have hit a plateau because cold weather is slowing the melt.

Fifteen communities have declared states of emergency and more than 400 people in two First Nations communities have been forced from their homes because of flooding.

Water continues to flow down Wascana Creek and into the engorged Qu'Appelle River, and the peak in Regina is still a week away.

The height of sandbag dikes around Wascana Creek in Regina is being raised. The city has already put 40,000 sandbags in place to protect low-lying areas. About 20,000 more sandbags have been filled and the city plans to fill another 20,000. 

"It's like a war zone here with everybody moving and stuff floating around," said Len Antal, who lives on Crooked Lake in the Qu'Appelle River valley. "Everybody down here has just been unbelievable helping each other out.

"If the wind ever picks up and the ice breaks up and starts to move, like really move, it'll just shear houses down like toothpicks."

Saskatchewan Premier Brad Wall said the province will do whatever it can to help prevent flood damage. His government earmarked $22 million in February to help communities design and build flood protection.

Wall predicted another $30 million might be required, but said Monday that communities and government ministries need to carry on their work without worrying about the cost right now.

In Alberta, the city of Medicine Hat remained under a state of emergency Monday, but elsewhere in the province, flooding appeared to be subsiding. Officials are still concerned, however, about the snowpack in the Cypress Hills border region with Saskatchewan. The snow has barely begun to melt and could carry torrents of water into area waterways.